1. Field of the Invention
The present invention relates to an ophthalmologic apparatus for taking an ophthalmic image used in an ophthalmologic hospital and the like and a control method thereof.
2. Related Background Art
In a conventional ophthalmologic image pickup apparatus, a nictitation detection function for optically detecting a state of an eyelid in an eye to be examined to detect whether the eye to be examined nictitated or not and for suspending an image pickup operation when the nictitation is produced is known.
However, according to the above nictitation detection function in the conventional example, a nictitation detection operation is performed at predetermined identical timing every time. Thus, in the case of a person to be examined which reacts to, for example, a click sound generated by an image pickup switch or a sound generated by moving an optical member to be inserted onto an optical path in synchronization with image pickup operation and thus unconsciously nictitates, there is a possibility that an image pickup error is continuously caused.
Also, in the case of a detector for detecting the state of an eyelid, it is extremely difficult to accurately determine the state of the eyelid because of an individual difference of reflectance of the eyelid, a difference of the amount of light from an observation light source, an influence of a cilia, and the like. Further, in the case where a special purpose light receiving element is used for detecting the state of an eyelid, when an influences of a cilia and the amount of observation light as described above, and the like are considered in addition to a variation in the sensitivity of the light receiving element, it is difficult to perform a work for adjusting the attachment position.
When the thus attached light receiving element is used, it is further difficult to perform a work for accurately detecting a state in which an eyelid is completely opened after a nictitation is produced. Thus, when the nictitation is detected one time, the image pickup operation must be suspended.
Also, in order to accurately adapt to a variation in the amount of observation light, a method of comparing the amount of incident light with the amount of reflecting light is considered. However, the number of light receiving elements with which the position adjustment is difficult is increased and thus a structure becomes complex and a cost becomes high.
An object of the present invention is to further improve a conventional ophthalmologic apparatus and to provide an ophthalmologic apparatus having an effect to an eye to be examined which unconsciously reacts to a sound generated by an image pickup operation to produce a nictitation while using an apparatus having a simple and low cost structure and a control method thereof.
Also, another object of the present invention is to provide an ophthalmologic apparatus capable of detecting a nictitation without almost depending on various parameters which influence detection precision by increasing a degree of freedom in an attachment position of a light receiving element and a control method thereof.
In order to attain the above-mentioned object, according to the present invention, there is provided an ophthalmologic apparatus having an image pickup device for taking an image of an eye to be examined and a controller for controlling the image pickup device, characterized in that the controller includes means for performing: a preparation step of detecting a completion of an image pickup preparation operation executed in accordance with an image pickup start signal for starting an image pickup for the image of the eye to be examined; an image obtaining step of obtaining the image of the eye to be examined; and a delay step of adding a delay time before the image obtaining step is started in accordance with a delay execution signal. Further, it is characterized in that the operation of the controller includes means for performing a detection step for detecting a nictitation of an eyelid.
Further objects of the present invention and structures thereof become clear in an explanation of the embodiments described below.